There is a small plastic fish that most of us have encountered without ever really thinking about it. It sits beside a takeaway sushi box, shaped like a salmon or a snapper, filled with a single portion of soy sauce, used for roughly thirty seconds before being tossed in the bin. It is so ordinary, so cheerfully designed, that its existence as a problem barely registers.
That is precisely what makes it such a useful example.
Eight to Twelve Billion Plastic Fish
The soy sauce fish, known in Japan as shoyu-tai or soy sauce snapper, was invented in the 1950s as a practical replacement for glass and ceramic bottles. It was a sensible solution to a real problem. The trouble is that the material it is made from outlasts its purpose by approximately five hundred years. Between eight and twelve billion of them have been used since the format was introduced. None of that plastic ever went anywhere. It broke down into smaller and smaller pieces, entered waterways, and is now found in places that should have nothing to do with takeaway sushi.
The irony of a fish shaped container contributing to ocean plastic is not lost on anyone who has thought about it for more than a moment.
A Better Fish
Australian design studio Heliograf, working with Vert Design, has produced Holy Carp!, a plastic free, compostable alternative made from bagasse pulp, a fibrous by product of sugar production. It looks almost identical to the original. It functions in the same way. It is leak resistant, holds soy sauce for up to 48 hours, and is designed to be filled directly by restaurants rather than relying on pre-packaged plastic alternatives.
The new container breaks down completely in four to six weeks, leaving no microplastics behind, and is made entirely without PFAS, the synthetic compounds sometimes called forever chemicals.
This is not a compromise. It is the same object, made better.
Why This Matters Beyond Sushi
The significance of Holy Carp! is not really about soy sauce. It is about a particular kind of design thinking that has been absent for too long.
The instinct, when faced with a wasteful product, is often to eliminate it entirely. Stop using plastic straws. Bring your own bags. Refuse the packaging. That instinct is right, but it has limits. Some products are genuinely embedded in how people eat, travel, and live. Asking people to simply go without is a blunt instrument. It works for some habits and fails for others.
What Heliograf have done instead is preserve the familiar object while replacing the material underneath it. The fish shape has become part of the cultural language of takeaway sushi. By preserving this visual identity while changing the material, the project demonstrates how design can intervene without disrupting everyday habits. The experience remains intact. The damage does not.
The Momentum Is Real
South Australia has already banned single use rigid plastic soy sauce containers under 30ml, with the ban taking effect from September 2025. Other Australian states are moving in the same direction. It would be naïve to assume the UK will not follow a similar path, given the trajectory of single use plastic legislation here over the past decade.
The plastic straw ban came in. The carrier bag charge changed behaviour in ways the sceptics did not anticipate. The direction of travel is clear, and for once, the commercial alternative is ready before the legislation forces the issue.
Small Objects, Large Principles
The soy sauce fish is a minor thing. That is partly what makes it a good lens for understanding how change actually happens.
Large systemic problems rarely get solved all at once. They get solved piece by piece, through hundreds of individual decisions by designers, manufacturers, restaurants, and consumers, each one replacing something harmful with something that works just as well without the damage. Progress rarely announces itself with grand gestures. More often it arrives looking almost identical to what it replaced.
A compostable fish beside your salmon maki is not going to fix the ocean. But it is evidence that the thinking is changing, and that when the thinking changes, the objects follow.
That is worth noticing.
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